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ESP32-C3 module

Espressif's low-cost Wi-Fi + Bluetooth LE RISC-V module with native USB. The WROOM-02 needs 3.3 V, a few capacitors, an EN delay and a BOOT button.

What it does#

The ESP32-C3-WROOM-02 is a complete Wi-Fi/BLE microcontroller: chip, 4 MB flash, crystal and PCB antenna under a shield. 15 usable GPIOs, USB Serial/JTAG on GPIO18 (D−) and GPIO19 (D+), so you can flash it over USB-C without a USB-serial chip.

Pins of the module: 1 3V3, 2 EN, 3–8 IO4–IO9, 9 GND, 10 IO10, 11 RXD, 12 TXD, 13 IO18, 14 IO19, 15 IO3, 16 IO2, 17 IO1, 18 IO0, 19 GND (pad).

What it needs (Espressif schematic checklist)#

  • 3.3 V, at least 500 mA (Wi-Fi transmit peaks), with 10 µF + 100 nF at the module. Supply range 3.0–3.6 V.
  • EN: 10 kΩ to 3V3 and 1 µF to GND (an RC delay, so the chip starts after the supply is stable) and a RESET button to GND. Never leave EN floating.
  • Strapping pins, read at reset:
Boot mode GPIO2 GPIO8 GPIO9
Normal (SPI boot) 1 any 1
Download (flashing) 1 1 0

So: pull-ups on GPIO2, GPIO8 and GPIO9, and a BOOT button from GPIO9 to GND. No big capacitor on GPIO9.

Example circuit: U1 with 10 µF + 100 nF, EN RC + RESET, GPIO9 pull-up + BOOT, GPIO2/GPIO8 pull-ups. USB_DN/USB_DP go to a USB-C block; unused pins carry no-connect marks.
U1 with 10 µF + 100 nF, EN RC + RESET, GPIO9 pull-up + BOOT, GPIO2/GPIO8 pull-ups. USB_DN/USB_DP go to a USB-C block; unused pins carry no-connect marks. Open the esp32c3_minimal example from this page in PCB Canvas: “Insert into my schematic”.

The ERC warns that USB_DN and USB_DP reach only one pin here: in a real design they continue to the USB-C and ESD block.

Pitfalls#

  • Antenna keep-out: no copper (pours included) under or around the antenna end; put that end at the board edge or past it.
  • Flashing: hold BOOT, tap RESET, release BOOT. With native USB, the chip usually re-enumerates by itself after that.
  • Espressif suggests reserving 22–33 Ω series resistors on D+/D−; small boards often skip them.

Sources: Espressif ESP32-C3 Hardware Design Guidelines, schematic checklist (power, CHIP_EN RC 10 kΩ/1 µF, strapping table, USB pins), and the ESP32-C3-WROOM-02 datasheet pin layout.

Footprint#

Castellated SMD module (C2934560, extended). Hand-solderable with patience; the ground pad underneath needs hot air or a via-and-solder trick.